The invention relates to a needleless injection instrument with a piston pump for injecting medium. The pump is connected to a drive motor. An operating element is displaceably fitted on the motor housing of the drive motor.
Injection instruments of the above type have been disclosed in U.S. Pat. Nos. 4,400,172 and 4,400,171.
It is an object of the present invention to provide these known injection instruments with a mechanism for counting the number of injections. The object is achieved by an injection instrument which comprises a stroke counter which is arranged in the motor housing and to the free shaft end of which a control cam is fixed which engages with a control pin supported on a control roll which is located in the operating element for the drive motor.